Influence of Isocyanate Structure on Recyclable Shape Memory Poly(thiourethane)

Area of Science:

• Polymer Chemistry
• Materials Science
• Biomaterials

Background:

• Shape memory polymers (SMPs) are advanced materials with the ability to recover their original shape when triggered.
• Poly(thiourethane)s (PTUs) offer tunable properties for various applications.
• Biodegradable materials are crucial for sustainable technological development.

Purpose of the Study:

• To synthesize and characterize novel poly(thiourethane)s (PTUs) with varying structures.
• To investigate the structure-property relationships governing shape memory behavior and biodegradability.
• To explore the potential of these PTUs in smart response applications.

Main Methods:

• Synthesis of PTUs via click chemistry using trimethylolpropane tris(3-mercaptopropionate) (S3) and various diisocyanates (HDI, IPDI, TDI).
• Fourier-transform infrared (FTIR) spectroscopy for reaction rate analysis.
• Shape memory property testing (shape recovery and fixity).
• Mechanical testing and in vitro degradation studies.

Main Results:

• TDI-based PTUs showed the fastest reaction rates due to conjugation and steric effects.
• All synthesized PTUs demonstrated excellent shape memory properties (over 90% recovery and fixity).
• Increased chain rigidity negatively impacted shape recovery and fixity but improved mechanical performance upon recycling.
• PTUs exhibited varying in vitro degradation rates, indicating potential as biodegradable materials.
• Contact angle measurements suggested potential for long-term or medium-term applications.

Conclusions:

• The study successfully synthesized PTUs with tunable properties and excellent shape memory.
• Chain rigidity is a key factor influencing shape memory performance and mechanical integrity after recycling.
• The biodegradability and tunable characteristics position PTUs as promising candidates for smart materials in artificial muscles, soft robots, and sensors.